Metallurgical vessel and method of operating same

ABSTRACT

A vessel for treating molten ferrous metal includes at least one tuyere for injecting process gases below the level of molten metal. The tuyere includes three pipes arranged in a concentric relation to define a first passage between the outer and intermediate pipes, a second passage between the intermediate and inner pipes and a third passage within the inner pipe. The pipes are sized to permit the volumetric percentage of gas delivered from the first passage to be about 2-10% of that delivered from the second and third passages and to permit the gas delivered from two of the passages to be about 15-60% of that delivered from the other passage. A quantity of metal is charged into the vessel for being preheated by the combustion of fuel delivered through a pair of passages and oxygen delivered through the remaining passage to provide an oxygen-to-fuel ratio which exceeds that required for stoichiometric combustion. After preheat and in preparation of the main blow, a shielding gas is delivered to the first passage and oxygen delivered through the inner two passages or the inner pipe is removed and oxygen provided through the interior of the intermediate pipe.

United States Patent Pearce et a1.

[ July 29,1975

1541 METALLURGICAL VESSEL AND METHOD OF OPERATING SAME [75] Inventors:Jai K. Pearce; Eberhard G.

Schempp, both of Pittsburgh; Walter Sieckman, Bridgeville, all of Pa.

[73] Assignee: Pennsylvania Engineering Corporation, Pittsburgh, Pa.

[22] Filed: June 15, 1973 [21] Appl. No.: 370,547

[52] US. Cl 266/35; 266/41 [51] Int. Cl. C211: 5/48 [58] Field of Search266/35, 36 P, 41; 75/51, 75/52, 59, 6O

[56] References Cited UNITED STATES PATENTS 985,394 2/1911 Case 266/41 X1,958,581 5/1934 Kennicott 266/35 X 2,676,012 4/1954 Luckey 266/413,209,810 10/1965 Schuvart 266/41 X 3,330,645 7/1967 Moustier et a1...266/35 X 3,547,624 12/1970 Gray 266/41 3,706,549 12/1972 Knuppel et al.266/35 X Primary Examiner-Gerald A. Dost Attorney, Agent, or Firm-FredWiviott [57] ABSTRACT A vessel for treating molten ferrous metalincludes at least one tuyere for injecting process gases below the levelof molten metal. The tuyere includes three pipes arranged in aconcentric relation to define a first passage between the outer andintermediate pipes, a second passage between the intermediate and innerpipes and a third passage within the inner pipe. The pipes are sized topermit the volumetric percentage of gas delivered from the first passageto be about 2-10% of that delivered from the second and third passagesand to permit the gas delivered from two of the passages to be about1560% of that delivered from the other passage. A quantity of metal ischarged into the vessel for being preheated by the combustion of fueldelivered through a pair of passages and oxygen delivered through theremaining passage to provide an oxygento-fuel ratiorwhich exceeds thatrequired for stoichiometric combustion. After preheat and in preparationof the main blow, a shielding gas is delivered to the first passage andoxygen delivered through the inner two passages or the inner pipe isremoved and oxygen provided through the interior of the intermediatepipe.

6 Claims, 5 Drawing Figures PATENTED JULZ 9 7 SHEET FUEL Q85 INERT GASMETALLURGICAL VESSEL AND METHOD OF OPERATING SAME BACKGROUND OF THEINVENTION This invention relates to pneumatic steel making vessels andprocesses of the type wherein process gases are blown beneath the levelof molten metal in a metallurgical vessel.

Converter vessels have been developed for treating molten metal by theinjection of oxygen or other gases directly into the molten metal bymeans of tuyeres located in the bottoms or sides of the vessels. Inorder to prolong the life of the vessels refractory and the tuyeresthemselves, each of the oxygen tuyeres may be surrounded by a secondtuyere for injecting a shielding fluid such as propane, manufacturedgas, natural gas, hydrocarbon gases or light oils. Depending upon thecomposition of the shielding fluid, the volumetric percentage of theshielding gas is normally about 2-10% of the volume of oxygen. As anexample, for an oxygen volume of about 200,000 standard cubic per hour,a propane shielding gas volume of about 6,000 standard cubic feet perhour would be required, while if manufactured gas is employed, therequired shielding gas volume would be about 14,000 standard cubic feetper hour. Tuyeres of this type normally comprise concentric pipes withthe oxygen being delivered through the inner pipe and the shielding gasbeing delivered in the annulus formed between the two tuyere pipes. Therelative sizes of the tuyere pipes are such as to permit the desiredratio of gases to be delivered.

In pneumatic steel making process, the vessel may be charged with hotmetal, scrap or a mixture of the two. When significant quantities ofscrap are employed, it may be necessary or desirable to preheat themetal prior to the initiation of the main oxygen blow. Heretofore, thishas usually been accomplished by auxiliary burners and lances.

SUMMARY OF THE INVENTION It is an object of the invention to provide anew and improved tuyere system for pneumatic steel making processes.

A further object of the invention is to provide a tuyere for pneumaticsteel making processes which may be employed both for preheating themetal charge and for the main oxygen blow.

These and other objects and advantages of the invention will become moreapparent from the detailed description thereof taken with theaccompanying drawings.

In general terms, the invention comprises a tuyere system for use inpneumatic metallurgical vessels and including a gas delivery means fordelivering oxygen beneath the level of the metallic charge in the vesseland passage means surrounding the gas delivery means for providing ashielding fluid around the oxygen input and means for subdividing thegas delivery means to permit an increase in the quantity of shieldingfluid provided through the tuyere system for preheating a molten metalcharge.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of ametallurgical vessel in which the tuyere system according to theinvention may be employed;

FIG. 2 illustrates the tuyere system according to the invention ingreater detail;

FIG. 3 illustrates an alternate embodiment of the present invention;

FIG. 4 shows yet another embodiment of the present invention; and

FIG. 5 shows a still further alternate embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. I schmatically illustratesan open hearth furnace 10 which may be employed with the systemaccording to the present invention. Vessel 10 generally includes arefractory shell 11 surrounded by a supporting framework generallydesignated by the reference numeral 12. The refractory lining 11generally defines a vessel having a shallow hearth 14 for containing thebath of molten metal 15. A plurality of charging openings 17 are formedalong one side of the vessel 10 and each is provided with a chargingdoor 18 which may normally be raised and lowered when desired in anysuitable manner. The vessel 10 may itself be mounted on stationaryconcrete or steel supports (not shown) or it may be mounted on rockers19 whereby the vessel may be tilted about an axis perpendicular to theplane of FIG. 1 for purposes of charging, pouring and deslagging. Aburner 20 may extend through one or both ends of the vessel 11 in amanner well known in the art.

A plurality of tuyeres 23 may extend through at least one side of thevessel 10 with their inner ends below the level of bath 15. As will bedescribed more fully below, the tuyere 23 will generally include a firstpassage for delivery of oxygen during the main oxygen blow and a secondpassage surrounding the first passage for injecting a shielding fluidsuch as propane, hydrocarbon gas, light oil, natural gas, and the like.As those skilled in the art appreciate, the shielding fluid prolongs therefractory and tuyere life. In addition to oxygen and propane, otherprocess gases such as argon and nitrogen may be blown through one orboth of the tuyere passages and finely divided materials such as lime,limestone, iron oxide, fluorspar, burnt lime and other materials may beentrained in the gas stream to provide the desired metallurgicalreactions.

In normal operation of the vessel 10, it will typically be charged withscrap and hot metal which must then be melted and/or preheated. Thetuyere system 23 according to the present invention, permits therequired ratio of fluids for both the preheat and main oxygen blowingperiods.

The tuyere assembly 23 according to the preferred embodiment of theinvention is shown in FIG. 2 to include three tuyere pipes 30, 32 and 34arranged in a coaxial relation. The inner diameter of the outermosttuyere pipe 30 is larger than the outer diameter of the intermediatetuyere pipe 32 to define a first gap or tuyere passage 36 therebetweenand the inner diameter of the intermediate pipe 32 is larger than theouter diameter of the innermost tuyere pipe 34 to define a second gap ortuyere passage 37 therebetween. A third tuyere passage 39 is defined bythe interior of the innermost tuyere pipe 34.

The tuyere pipes 30, 32 and 34 are mounted in spaced apart relation bymeans of a hollow, generally tubular tuyere pipe support body 40. Asseen in FIG. 2, the body 40 is formed with a cylindrical bore 42intermediate its ends and to which the outer end of the intermediatetuyere pipe 32 is secured in any suitable manner, such as by welding. Atthe vessel end of the body 40, a counter-bore 44 is formed for fixedlyreceiving the end of the outermost tuyere pipe 30. In this manner, thetuyere pipes and 32 are affixed in spaced relation to form the gap 36.At the opposite end of the body 40, a concentric, smaller diameteropening 46 is formed for slidably receiving the innermost tuyere pipe 34therethrough. In addition, a radially outwardly extending flange 47 isformed on the body adjacent opening 46 for mating with a similarlyconfigured radial flange 49 affixed to tuyere pipe 34. The flanges 47and 49 may be secured in any suitable manner such as by bolts 50 andnuts 52. This positions the innermost tuyere pipe 34 in spaced relationfrom the intermediate tuyere pipe 32 to define the gap 37 therebetween.

An external gas connection is provided to the tuyere passage 36 by meansof a pipe 54 having a threaded end which is received in an internallythreaded aperture 55 formed through body 40 adjacent the end of tuyerepipe 30. An annular groove 57 may also be formed in bore 42 and in anintersecting relation to the inner end of aperture 55. A similarexternal gas connection is provided to the tuyere passage 37 by means ofa pipe 58 which is threaded into aperture 60 formed in body 40 adjacentthe end of tuyere pipe 32 and an annular groove 61.

The tuyere assembly 23 may be supported on the vessel 10 in any suitablemanner such as by means of a first mounting member 63 affixed to body40, a second mounting member 64 affixed at one end to member 63 and atits other end to a mounting plate 65 which is secured to the vessel 10by means not shown. The first mounting member 63 includes a hollow bodyportion 67 which is affixed at one end of the vessel end of body 40 andin a concentric surrounding relation to the outer tuyere pipe 30. Aradially extending flange 68 is integrally formed at the other end ofbody member 67 for being secured by bolts 70 and nut 72 to a similarflange 73 which extends integrally from one end of the hollow bodymember 64. The other end of the body 64 is secured in a concentricsurrounding relation to an aperture 75 formed in plate 65. Aperture 75is sized to receive tuyere 30 therethrough and the latter extendsthrough vessel refractory 11 with the ends of pipes 30, 32 and 34opening into vessel 10 and beneath the level of the charge 15.

When the vessel 10 is to be placed in operation, it will initially becharged with hot metal and scrap through charging doors 17. In order toraise the temperature of the metal charge 15 to that necessary prior tothe beginning of the main oxygen blow, a melt down and/or preheat periodwill initially commence. In order to employ the tuyere 23 as a preheattorch, it is desirable to provide oxygen and fuel in such proportionsthat the oxygen fuel ratio will be slightly greater than that requiredfor stoichiometric combustion. Toward this end, a fuel such as propanewill be delivered through pipe 54 to the outer tuyere passage 36 andoxygen will be delivered to tuyere passage 37 through pipe 58. Inaddition, the propane or other fuel will be provided through the innertuyere pipe 39. By proportioning the relative sizes of the tuyere pipes30, 32 and 34, the correct proportions of fuel and oxygen will beprovided. With the fuel volume being approximately 15-60% that of theoxygen, depending on the fuel employed.

After the completion of the melt down or preheat period, it is desirableto commence the main oxygen blow during which the oxygen is to bedelivered to the bath through a center jet surrounded by an outer sheathof shielding fluid which is provided to prolong the life of the tuyeresand their surrounding refractory. During the main oxygen blow, thevolume of shielding fluid required is about 2-10% of the volume ofoxygen depending upon the fluid to be employed. For example, if propaneis used, the shielding gas volume should be about 3% of the oxygenvolume. In order to provide the greater volume of oxygen requiredaccording to the preferred embodiment of the invention, the centermosttuyere pipe 34 is removed by removing nuts 52 and bolts 50 andwithdrawing tuyere pipe 34 along with flange 49. The opening 46 in body40 is then closed in any suitable manner such as by means of a plate 78.The main oxygen blow may then commence with the shielding gas beingprovided to the passage 36 through pipe 54 and the oxygen being providedto the interior of pipe 32 through pipe 58.

An alternate embodiment of the invention is shown in FIG. 4 wherein anoxygen source is shown to be connected to pipes 34 and 58 through valves82 and 83 respectively. In addition, a source of hydrocarbon fuel, suchas propane 85 is respectively connected to pipes 54 and 34 throughvalves 86 and 87. Also, a source of inert gas such as argon or nitrogenis connected to pipe 34 through valve 89. During the preheat period, asdiscussed above, the valve 83 is opened to deliver oxygen to pipe 58 andvalves 86 and 87 are opened to deliver propane to pipes 34 and 54.Valves 82 and 89 are closed. This provides fuel to the tuyere passages36 and 39 and oxygen to the tuyere passage 37 as discussed above. At thecompletion of the preheat period, and prior to the commencement of themain blow, valves 83, 86 and 87 are closed and valve 89 is opened topurge the pipe 39 of propane. Thereafter, valves 82 and 83 are opened toprovide oxygen to the tuyere passage 37 and 39 and valve 86 is opened toprovide propane to the outer tuyere passage 36. In this manner, it ispossible to proceed from the preheat to the main blow without physicallyremoving the center tuyere pipe 34.

FIG. 5 illustrates a still further embodiment of the invention whereinan outer tuyere pipe 30' is disposed in concentric surrounding relationto a central tuyere pipe 32 to define a gap 36 therebetween. The gap 36is sized to provide the correct proportion of shielding gas to oxygenduring the main oxygen blow. The pipe 32 is subdivided by a longitudinalpartition wall 92 to divide the interior of pipe 32' into passages 93and 94. During the warmup period, the tuyere passages 36' and 94 may beprovided with a fuel such as propane through the pipes 54 and 39 and thepassage 93 may be provided with oxygen through pipe 58. At thecompletion of the preheat period, a gas supply and valve system similarto that shown in FIG. 4 may be employed to first purge pipe 94 ofpropane and then to provide passages 93 and 94 with oxygen and passage36 with the hydrocarbon shielding fluid for the main oxygen blow.

While only a few embodiments of the invention have been shown anddescribed, it is not intended to be limited thereby but only by thescope of the appended claims.

We claim:

1. A metallurgical vessel constructed and arranged to receive a metalliccharge,

a tuyere assembly including first means defining a first tuyere passagefor delivering oxygen to the interior of said vessel and beneath thelevel of said charge,

second means for defining a second tuyere passage in surroundingrelation to the first tuyere passage for providing a hydrocarbonshielding fluid around the oxygen, third means for subdividing the firsttuyere passage into a pair of tuyere passages to permit an increase inthe quantity of shielding gas provided to the tuyere for preheating ametal charge in the vessel,

a source of hydrocarbon fluid and a source of oxyfirst valve means forselectively coupling said oxygen source to one of said pair of tuyerepassages and said hydrocarbon fluid source to said second tuyere passageand second valve means for selectively coupling one of said sources tothe other of said pair of tuyere passages.

2. The vessel set forth in claim 1 and including a source of an inertgas, third valve means operative to selectively couple said inert gassource to the other of said pair of tuyere passages prior to theoperation of said second valve means to purge said other one of saidpair of tuyere passages before the same is coupled to the other one ofsaid sources.

3. The vessel set forth in claim 2 wherein said second tuyere passage issized to provide a fuel volume which is about 2% to of the volume ofoxygen provided through said pair of tuyere passages, said pair oftuyere passages being sized to provide a total fuel volume substantiallygreater than 10% of said oxygen volume when said second valve meanscouples the other one of said tuyere passages to said source ofhydrocarbon fluid.

4. The vessel set forth in claim 3 wherein said third means is removablydisposed in said first tuyere means, and tuyere body means for mountingsaid tuyere assembly to said vessel, said tuyere body means having anopening formed therein for receiving said third means therethrough, andclosure means for said opening after removal of said third means.

5. The vessel set forth in claim 1 wherein said first means comprises afirst tuyere pipe defining said first tuyere passage and said secondmeans comprises a second tuyere pipe disposed in closely surroundingrelation and spaced from said first tuyere pipe to define said secondtuyere passage, said third means comprising a third tuyere pipeinsertable into said first tuyere pipe and having an outer surfacespaced from the inner surface of said first tuyere pipe when mountedtherein to define therewith one of said pair of tuyere passages, theinner surface of said third tuyere pipe defining the other of said pairof tuyere passages, securing means for removably securing said thirdtuyere pipe in said first tuyere pipe.

6. The vessel set forth in claim 5 wherein said first tuyere pipe has anopen end external of said vessel said securing means being operable tosecure said third pipe means in said open end for sealing the same, andcover means for closing said open end after removal of said third pipemeans.

1. A metallurgical vessel constructed and arranged to receive a metalliccharge, a tuyere assembly including first means defining a first tuyerepassage for delivering oxygen to the interior of said vessel and beneaththe level of said charge, second means for defining a second tuyerepassage in surrounding relation to the first tuyere passage forproviding a hydrocarbon shielding fluid around the oxygen, third meansfor subdividing the first tuyere passage into a pair of tuyere passagesto permit an increase in the quantity of shielding gas provided to thetuyere for preheating a metal charge in the vessel, a source ofhydrocarbon fluid and a source of oxygen, first valve means forselectively coupling said oxygen source to one of said pair of tuyerepassages and said hydRocarbon fluid source to said second tuyere passageand second valve means for selectively coupling one of said sources tothe other of said pair of tuyere passages.
 2. The vessel set forth inclaim 1 and including a source of an inert gas, third valve meansoperative to selectively couple said inert gas source to the other ofsaid pair of tuyere passages prior to the operation of said second valvemeans to purge said other one of said pair of tuyere passages before thesame is coupled to the other one of said sources.
 3. The vessel setforth in claim 2 wherein said second tuyere passage is sized to providea fuel volume which is about 2% to 10% of the volume of oxygen providedthrough said pair of tuyere passages, said pair of tuyere passages beingsized to provide a total fuel volume substantially greater than 10% ofsaid oxygen volume when said second valve means couples the other one ofsaid tuyere passages to said source of hydrocarbon fluid.
 4. The vesselset forth in claim 3 wherein said third means is removably disposed insaid first tuyere means, and tuyere body means for mounting said tuyereassembly to said vessel, said tuyere body means having an opening formedtherein for receiving said third means therethrough, and closure meansfor said opening after removal of said third means.
 5. The vessel setforth in claim 1 wherein said first means comprises a first tuyere pipedefining said first tuyere passage and said second means comprises asecond tuyere pipe disposed in closely surrounding relation and spacedfrom said first tuyere pipe to define said second tuyere passage, saidthird means comprising a third tuyere pipe insertable into said firsttuyere pipe and having an outer surface spaced from the inner surface ofsaid first tuyere pipe when mounted therein to define therewith one ofsaid pair of tuyere passages, the inner surface of said third tuyerepipe defining the other of said pair of tuyere passages, securing meansfor removably securing said third tuyere pipe in said first tuyere pipe.6. The vessel set forth in claim 5 wherein said first tuyere pipe has anopen end external of said vessel said securing means being operable tosecure said third pipe means in said open end for sealing the same, andcover means for closing said open end after removal of said third pipemeans.